1. Field of the Invention
The present invention relates to a probe structure for testing semiconductor devices. More particularly, the present invention relates to a probe structure for testing semiconductor devices, which is fabricated by a series of semiconductor fabrication process which can be finely controlled. Therefore, the probe structure for testing semiconductor devices according to the present invention satisfies the high density of the probe structures, the uniformity of size, height and spacing of the probe structures, and the integration of the probe structures, thereby maximizing efficiency of the test process of the semiconductor devices. Further, the present invention relates to a method for fabricating the probe structure for testing semiconductor devices.
2. Description of the Related Art
As well known to those skilled in the art, prior to a packaging process, semiconductor devices on a wafer are tested. In this testing step, a probe structure including a plurality of needles is mounted on a testing equipment. Then, the semiconductor devices are inspected using the testing equipment, thereby detecting defective products generated by mistakes of the fabrication process of the semiconductor devices.
Herein, the probe structure, which comes in contact the semiconductor device, serves to transmit test signals from the external testing equipment to the semiconductor device, or to transmit output signals from the semiconductor device to the external testing equipment.
Since the probe structures intermediate between the external testing device and semiconductor device, the characteristic of the probe structure is very important parameter that may affect the reliability of test process for semiconductor devices. Therefore, researches on probe structure have been extensively performed.
For example, U.S. Pat. No. 4,563,640 entitled xe2x80x9cFixed probe boardxe2x80x9d, U.S. Pat. No. 5,070,297 entitled xe2x80x9cFull wafer integrated circuit testing devicexe2x80x9d, U.S. Pat. No. 5,172,050 entitled xe2x80x9cMicromachined semiconductor probe cardxe2x80x9d, U.S. Pat. No. 6,072,321 entitled xe2x80x9cMicromachined silicon probe card for semiconductor device and method of fabricationxe2x80x9d, and U.S. Pat. No. 5,475,318 entitled xe2x80x9cMicroprobexe2x80x9d disclose representative conventional probe structures.
However, these conventional probe structures still have many problems, as follows.
For instance, a probe card as disclosed in the aforementioned U.S. Pat. No. 4,563,640 is manufactured by assembling a plurality of metal needles by hand, thereby causing several problems such as long assembly time and high assembly cost. Further, it is difficult to regulate the exact position and the height of the needles. Therefore, a worker should frequently re-adjust the position or the height of the needles.
That is, since it is difficult to integrate a plurality of needles on the probe card, the probe card tests only a small fraction of the integrated circuit chips on a semiconductor wafer, thereby increasing time for testing a full wafer including the chips.
Therefore, in order to simultaneously test tens of semiconductor wafers manufactured a day, plural test equipments are required.
The aforementioned U.S. Pat. No. 5,070,297 discloses a testing device comprising probe tips made of metal, which are mounted on a flexible polyimide base. Compared with U.S. Pat. No. 4,563,640, the integration can be easily obtained.
However, it is difficult to control the residual stress of the polyimide layer and the mechanical characteristics of the metal probe tips. Therefore, because of these drawbacks, the testing device of this patent cannot be easily used in the testing step of the wafer including the integrated circuit chips.
Further, the aforementioned U.S. Pat. No. 5,172,050 discloses a probe card formed by bulk micromachining a single crystalline silicon. The probe card comprises micromachined probe beams and probe tips rested on the probe beams. In this patent, it is not easy to bulk-micromachine the probe beams with conventional techniques. Further, since there is a separate process of resting the probe tips on the probe beams, the whole process is complicated and it is difficult to maintain the mechanical stability of the probe tips. Another problem is that test pads of the semiconductor device must be newly designed corresponding to the shapes of the probe beams and probe tips of the probe card.
The aforementioned U.S. Pat. No. 6,072,321 discloses a membrane probe card including silicon/metal thin film probe tips formed thereon. Compared with the earlier patents, the mechanical stability of the probe tips of this patent can be easily obtained. However, since the membrane probe card of this patent does not comprise means for providing sufficient contact forces between the probe tips and the test pads of the semiconductor device, a fluid for applying a pressure to the membrane might be required. This might cause the worker inconvenience.
Finally, the aforementioned U.S. Pat. No. 5,475,318 discloses a microprobe with a bimorph structure of a double layer comprising aluminum and silicon layer, and an integrated heating element made of polysilicon. The microprobe is actuated by the heat supplied from the heating element, thereby coming in contact with the semiconductor device. In this case, it is difficult to integrally fabricate the probe beam, the probe tip and the heating element. Further, since the microprobe is formed by depositing a thin film, the microprobe is affected by residual stress and stress gradient of the membrane. Therefore, it is difficult to maintain the mechanical stability of the microprobe. Moreover, in addition to signal lines for providing interface with the semiconductor devices, a signal line for driving the heating element is required, thereby complicating peripheral circuits.
In view of the foregoing problems associated with conventional probe structures for testing semiconductor devices, there is a need for a probe structure with improved functions.
Therefore, the present invention has been made in view of the above problems, and it is an object of the present invention to finely control a fabricating process of a probe structure, thereby solving the problem of long fabrication time and the difficulty in finely controlling the structure of the probe structure.
It is a further object of the present invention to perform the fabricating process of the probe structure on a single bulk substrate, thereby achieving uniform size, height, and spacing of the probe structures assembled in one unit.
It is another object of the present invention to increase the density of the probe structure, thereby simultaneously testing a full wafer or a very large fraction of the integrated circuit devices on a semiconductor wafer, and solving the problems such as lengthened testing time and having to newly design the test pads of the semiconductor device according to the shapes of probe beams and probe tips of the probe structure.
It is still another object of the present invention to integrate the probe structure, thereby solving the difficulty in performing the contact between the probe structure and the semiconductor device due to non-uniformity of size, height and spacing of the probe structures.
It is yet another object of the present invention to unify the whole structure of the probe structure, thereby simplifying the process and stabilizing the mechanical characteristics of the probe structure.
In accordance with the present invention, the above and other objects can be accomplished by the provision of a probe structure for testing semiconductor devices. The probe structure comprises a base substrate, a protrusion formed integrally with the base substrate, probe beams branching off from the protrusion, and probe tips rested on the ends of the probe beams.
Herein, the protrusion is protruded from the upper surface of the base substrate at a designated angle, and extends along the upper surface of the base substrate. The probe beams are positioned above the upper surface of the base substrate, and extend along the upper surface of the base substrate in a different direction, preferably perpendicular direction, to the extension of the protrusion. The probe tips are protruded from the upper surface of the base substrate, and mechanically and electrically come in contact with the test pads of the semiconductor device.
The probe structure of the present invention is manufactured via the semiconductor fabrication process which can be finely controlled, and the fabricated probe structure satisfies the high density, the uniformity of size, height and spacing, and the integration of elements, thereby solving the conventional problems such as unnecessary increase in fabrication time of the probe structure, difficulty in finely controlling the structure of the probe structure, complexity of the whole process, mechanical instability of the products, and difficulty in uniformly assembling a plurality of the probe structures. Additionally, the probe structure of the present invention solves several problems caused in an actual testing step of the semiconductor devices, for instance, small-scale of testing process for semiconductor device, lengthening of testing time of the semiconductor device, difficulty in providing the sufficient contact force between the probe structure and the semiconductor device, and having to newly design the test pads of the semiconductor device according to the shapes of the probe beams and probe tips of the probe card.